HT4100 4.1, 4.5, 4.9 Discussion, The "4.9 liter turbocharger, stage 1" thread. in Cadillac Engine Technical Discussion; Hey Crazy, my turbo is worse off than that one! On mine, there is a 6 as the last part ...

Re: The "4.9 liter turbocharger, stage 1" thread.

Shit I was hoping to get an accurate number from you. I don't know if you realize/understand how important a compressor map is? I am trying to figure out as accurate as possible the choke/surge line for this turbo on a different motor than intended. Sure it's been done on on the 4.9 motor but to my knowledge wasn't intended for this motor correct?

An ill suited turbo can choke at low rpm and surge at high rpm, I am trying to avoid this for both of our sakes and find a happy medium where the turbo operates most efficiently based on the fact that we're both running two entirely different motors than intended.

I know that it has been done on that Fiero, but I don't see any type of A/F ratio or dyno slips posted a long with it. All I see is one mediocre 12 second 1/4 mile time and subsiquent selling of the motor or a plan to "remove it and put it in storage"

In essense, this really does or says nothing in terms of reliability. All it says is that this guy bolted one on and pushed the peddle on the right to the ground. It says nothing about whether or not it can/will last or that it was done correctly, or that the 12 second run can be replicated.

Shit, I've posted a 12 second run with half the pistons and half the turbo.

What I'm saying is that although this has been done, it doesn't seem to have done correctly, only bolted on and that is easy to do.

Replicating an insanely high dyno or a sub 10 second quarter mile more than once is not, which I'm sure isn't your intention, mine either.

Re: The "4.9 liter turbocharger, stage 1" thread.

Originally Posted by CallMeCrazy

Shit I was hoping to get an accurate number from you. I don't know if you realize/understand how important a compressor map is? I am trying to figure out as accurate as possible the choke/surge line for this turbo on a different motor than intended. Sure it's been done on on the 4.9 motor but to my knowledge was intended for this motor correct? An ill suited turbo can choke at low rpm and surge at high rpm, I am trying to avoid this for both of our sakes and find a haoppy medium where the turbo operates most efficiently based on the fact that we're both running two entirely different motors than intended.

I know that it has been done on that Fiero, but I fail to see any type of A/F ratio or dyno slips posted a long with it. All I see is one mediocre 12 second 1/4 mile time and subsiquent selling of the motor or a plan to "remove it and put it in storage"

In essense, this really does or says nothing in terms of reliability. All it says is that this guy bolted one on and pushed the right peddle to the ground, it says nothing about whether or not it can/will last or that it was done correctly, or that the 12 second run can be replicated.

Shit, I've posted a 12 second run with half the pistons and half the turbo.

What i'm saying is that although this has been done, it doesn't seem to have done correctly, only bolted on and that is easy to do.

Replicating an insanely high dyno or a sub 10 second quarter mile is not.

When I get my turbo installed and blow the motor, I'll let you know how it works.

Re: The "4.9 liter turbocharger, stage 1" thread.

lol I'm sure that isn't what you want either. All I meant is that I'm more into the scientific aspect which goes hand in hand with reliablity. If you do it right, it will last. If you do it wrong, you might get one 12 second pass and melt/crack a piston or two. That's the type of situation I am trying to avoid, which I'm sure you are too. All I'm saying is that it would 've been nice to get some accurate A/F ratios/dyno slips with realtime A/F ratio from that guy rather than "I bolted it on, now I'm removing it and selling it" know what I mean?

If you happen to know of any dyno slips with the boost pressure stated, it would help out immensly. I could use it to find out CFM or lbs/min of the turbo based on CID of an N/A engine vs FI with this turbo.

I'll be sure to post when I get some more info. Good luck with your project.

Re: The "4.9 liter turbocharger, stage 1" thread.

So going by your motor which is 4,900cc or roughly 299 cid (not sure what your redline is??)

(CID × RPM????) ÷3456 = CFM

(299 × say 6000?) ÷ 3456 = 519.10 CFM

The engine will flow 519.10 CFM of air assuming a 100% volumetric efficiency and assuming a common redline of 6K. Most street engines will have an 80-90% VE.

519.10 × 0.85 = 441.23 CFM

Your 299 cid would flow 441.23 CFM with an 85% VE. A good rule of thumb is that for every 10 hp a gasoline engine makes, it needs roughly a lb of air/min delivered to the intake manifold, so, you'd multiply 441.23 CFM by .07 giving you 30.89 lbs/min and putting your motor at roughly 300 hp naturally aspirated, am I right?

Add in pressure ratio, you said 6-8 psi?

(6 + 14.7) ÷ 14.7 = 1.41:1 pressure ratio. Looking back at the RHC6 chart, you'd be operating on the low end, BUT, I still haven't figured out the density ratio. If you give me your redline and your plans for the motor (how much are you looking to get out of it and at what boost level?) I can figure out where the turbo operates most efficiently.

I still need to come up with a compressor map, but bear with me, I have a lot going on right now.

I was useing stupid math myself ...i said hey , this turbo will produce enough to make 7psi at 8,000 rpm in a sr20det ...so it should be good enought o pull 7 psi at 4500 rpm on 5.0 liters (twice the air going thru at half the rpm ?)...

if you want to know what i REALLY want to do ....look no further than the paxtons sitting on 5 liter mustangs

Re: The "4.9 liter turbocharger, stage 1" thread.

My point early on in this thread is with a high compression 4.9L, you DON'T want to make it efficient until high rpm. The high compression and boost will destroy weak pistons like 4.9's have. Be careful. I would recommend not hitting more than 2-3 psi until above 3500-4000 rpm.

Unless you drop the compression I don't feel you will ever have a good running 4.9 Turbo.

Re: The "4.9 liter turbocharger, stage 1" thread.

So going by your motor which is 4,900cc or roughly 299 cid (not sure what your redline is??)

(CID × RPM????) ÷3456 = CFM

(299 × say 6000?) ÷ 3456 = 519.10 CFM

The engine will flow 519.10 CFM of air assuming a 100% volumetric efficiency and assuming a common redline of 6K. Most street engines will have an 80-90% VE.

519.10 × 0.85 = 441.23 CFM

Your 299 cid would flow 441.23 CFM with an 85% VE. A good rule of thumb is that for every 10 hp a gasoline engine makes, it needs roughly a lb of air/min delivered to the intake manifold, so, you'd multiply 441.23 CFM by .07 giving you 30.89 lbs/min and putting your motor at roughly 300 hp naturally aspirated, am I right?

Add in pressure ratio, you said 6-8 psi?

(6 + 14.7) ÷ 14.7 = 1.41:1 pressure ratio. Looking back at the RHC6 chart, you'd be operating on the low end, BUT, I still haven't figured out the density ratio. If you give me your redline and your plans for the motor (how much are you looking to get out of it and at what boost level?) I can figure out where the turbo operates most efficiently.

I still need to come up with a compressor map, but bear with me, I have a lot going on right now.

The redline for the 4.9 liter is 5200 RPM's. As for the amount of boost, I want no more than 6 psi when all is said and done.

Basically I would like to add a few hp above the 4100 RPM line, and not let boost come on till about the 2500 RPM line. I'll scan over everything you've supplied and see if I can't do the compressor map myself for my particular turbocharger. But please, feel free to beat me to it...

Originally Posted by N0DIH

My point early on in this thread is with a high compression 4.9L, you DON'T want to make it efficient until high rpm. The high compression and boost will destroy weak pistons like 4.9's have. Be careful. I would recommend not hitting more than 2-3 psi until above 3500-4000 rpm.

Unless you drop the compression I don't feel you will ever have a good running 4.9 Turbo.

Tom is right Stoney. We want the high end power and keep the natural low end torque for now. I just hope this diesel turbo does the trick...

As for the compression ratio, I've thought about taking the heads off and giving some more room in the combustion chamber area. That should lower it some...

Re: The "4.9 liter turbocharger, stage 1" thread.

alright, so the 5,200 rpm redline changes things a little bit. ( I still need to know the exact CID of your 4.9?)

299 x 5200/3456=449.88 @100% VE which is nearly impossible naturally aspirated.
299 x 5200 x .85/3456 =382.40 @ 85% VE which is more realistic. You CAN however have more than 100% VE with the addition of a well thought out turbo and efficient intercooling.

An 85% VE of 382.40 x .07=26.77 lbs/min

26.77 x 1.41 Pr=37.75 lbs/min under 6 psi of boost. If you give me your compression ratio I can figure out what it would be under 6 psi of boost as well.

Here are some things I still need to figure out a compressor map:
1) What engines came with this turbo?
2) Of those engines, are they ALL turbo charged or are some naturally aspirated?

Assuming that some are naturally aspirated, I need to find out what their CID is and estimated HP and TQ at various rpms. I'll also need the same info for the turbocharged versions as well as how many lbs of boost the turbos run stock? With this info, I can figure out the % difference between the N/A and FI in VE vs HP/TQ in all models and come up with a realistic equationf of how much CFM/lbs/min the turbo must push.

Re: The "4.9 liter turbocharger, stage 1" thread.

Originally Posted by CallMeCrazy

alright, so the 5,200 rpm redline changes things a little bit. ( I still need to know the exact CID of your 4.9?)

299 x 5200/3456=449.88 @100% VE which is nearly impossible naturally aspirated.
299 x 5200 x .85/3456 =382.40 @ 85% VE which is more realistic. You CAN however have more than 100% VE with the addition of a well thought out turbo and efficient intercooling.

An 85% VE of 382.40 x .07=26.77 lbs/min

26.77 x 1.41 Pr=37.75 lbs/min under 6 psi of boost. If you give me your compression ratio I can figure out what it would be under 6 psi of boost as well.

Here are some things I still need to figure out a compressor map:
1) What engines came with this turbo?
2) Of those engines, are they ALL turbo charged or are some naturally aspirated?

Assuming that some are naturally aspirated, I need to find out what their CID is and estimated HP and TQ at various rpms. I'll also need the same info for the turbocharged versions as well as how many lbs of boost the turbos run stock? With this info, I can figure out the % difference between the N/A and FI in VE vs HP/TQ in all models and come up with a realistic equationf of how much CFM/lbs/min the turbo must push.

If you guys can find me this info it would help immensly.

The exact displacement of the 4.9 liter is 300 cubes. No more, no less. Sorry I didn't post that earlier.

Compression ratio is a concern for this engine: 9.5:1 ratio. I've long thought about lowering it via machining the combustion chamber area on the heads.

As for the turbocharger, it is from the GM diesel 6.5 liter engine. My particular turbo is a GM3 from a '93-'94 Suburban 2500 series that had the turbodiesel engine. As far as I know, those engines were the only ones unber boost. The gas engines used in those autos were the Chevy 350 engine and a 7.4 liter variant. Otherwise, it was the turbodiesel 6.5 liter. The output for this engine was around 190 hp...Not sure at what RPM's though and I cannot find torque rating either.

Let me know if I need that stuff, and I'll attempt to dig it up again.

Re: The "4.9 liter turbocharger, stage 1" thread.

So far the boost pressure is at 7 psi stock without intercooling for the GM 6.5 liter turbodiesel engines. I still can't find the redline information, but wouldn't it be safe to assume that the redline on these engines is just a few hundred RPM's over base hp ratings? Just a thought.